1. Field of the Invention
This invention relates to liquid appliances and, more particularly, to an electric percolator or other liquid heating devices.
2. Description of the Prior Art
Glass receptacles have long been favored in the food preparation field because of the advantages in sanitation and appearance offered by this material. Another substantial advantage of transparent glass is that the user of the appliance can easily observe the contents without opening the receptacle. However, glass has inherent disadvantages which make it less than an ideal material for the manufacturing of appliances. Glass cannot be formed or shaped as easily as metal materials, nor can it be joined easily with other materials to form complex shapes which are often found desirable for cooking appliances. One of the reasons for this problem is that glass cannot be economically mass produced to close tolerances, and the variations in the size of the glass items produced make joining glass items with any other items relatively difficult. Also, of course, glass is a relatively fragile material and, accordingly, glass items usually have a relatively high rate of breakage, especially during manufacturing processes which require extensive handling of the glass item.
To date, two main methods have been used for joining a glass item with another item to form a composite assembly. These methods are either gluing the glass to the other item or strapping the glass to the other item. The disadvantages offered by gluing are substantial. Gluing is a relatively slow process, very often too slow for efficient mass production of an item. Additionally, gluing often requires clamping to insure a strong bond between the elements to be joined, but this clamping imparts stresses to the glass which may crack or shatter the glass during the production process or later on during normal use of the article.
Using bands to bind elements to glass also presents the problem of stresses imparted to the glass by the band. These bands are usually made of very strong and hard substances, such as stainless steel, which cannot completely conform to the surface they surround. Therefore, irregularities in the surface of the glass around which the band is applied result in less than a complete contact of the band surface with the glass. This incomplete contact produces stress concentration points on the glass at the points of contact with the band.
Additionally, the lack of complete contact between the band surface and the glass produces a rocking or loose fit between the elements which tends to make the use of the article somewhat uncertain in the mind of the user.
Lastly, the space between the glass and the band provides areas where seepage and/or leakage can occur.
Other problems have been uniquely present in relation to the construction of electric percolators or other vessels used for heating food in closed containers. In almost all of these vessels, the tops must be quickly removable in order to obtain easy access to the inside of the vessel, but at the same time the tops must be securely held in place so that they cannot fall off when liquid, for example, is being poured from the vessel. Obviously, if the top were to fall off during the pouring of liquid, serious safety hazards would be involved. Nevertheless, almost all of the tops are secured by mechanisms which require a lifting of the top from the vessel in order to remove the top. Therefore, the same forces which act against the top when the vessel is tipped to pour liquid also tend to move the top from the vessel. Further, since a lifting motion is required, very often the vessel is lifted off the surface on which it is resting when the top is sought to be removed and the vessel is dropped, or worse, inadvertently slammed down on the resting surface when the top is separated from the vessel.
Another problem has been apparent in connection with the manufacture of electrical percolators, and that is the circuitry necessary for indicator lights which show the user of the percolator when the percolator is in the rapid heating mode for brewing of coffee or liquid as compared to when it is in the "keep warm" mode or phase of operation. In the past, normal practice has been to use two indicator lights in combination to accomplish this purpose; one or both indicator lights operating brightly when the apparatus is operating in its heating mode, and a second light operating when the apparatus is in the keep warm or lower heating mode of the apparatus.